A gas turbine blade can be cast of a high-temperature metal alloy in the form of a single crystal per blade to maximize strength. It is difficult and expensive to reliably cast an integral platform in a single-crystal blade casting, due to the complexity of the blade/platform shape and the corresponding complexity and size of the casing mold. Therefore, non-integral platforms have been attached to the turbine disk between blades.
For example, U.S. Pat. No. 4,621,979 shows non-integral platforms mounted by a pin and hinge structure. In this patent, a relatively simple blade shape is shown. However, modern turbine blades have a high pitch angle relative to the turbine axis, and high camber and thickness. This geometry requires a platform with a complex asymmetric perimeter, which complicates designing a platform that can be mounted and replaced between the blades. Axial mounting would require a very narrow platform of constant curvature. Radial mounting is difficult regarding sealing around the platform edges, and limiting asymmetric cantilevered centrifugal stress on the platform.
The present invention solves these problems. It allows the platforms to be mounted and removed radially, and to be sealed without removing any blades, thus providing fast platform replacement.